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Contents

• Cellular Senescence as a Contributing Cause of Sarcopenia
• Continued Exploration of Age-Related Differences in the Human Gut Microbiome
• Naked Mole Rats Exhibit Minimal Cardiac Aging
• Autophagy in the Context of Immune System Aging
• Two Years of Calorie Restriction Produces Thymic Regrowth in Humans
• Gene Therapy Delivering the Longevity-Associated Variant of BPIFB4 Improves Immune Function in Old Mice
• Activated Protein C Activity is Impaired in Aging Hearts, Leading to Greater Vulnerability to Ischemia
• Aquaporin-4 Expression in the Aging Choroid Plexus
• Improved Physical Function in Old Mice Treated with Rapamycin, Acarbose, and Phenylbutyrate
• More Animal Study Evidence for Senolytics to Improve Cognitive Function in Old Age
• 25-Hydroxycholesterol as a Basis for Senolytic Therapy
• Early CAR-T Therapies Produced Long Term Remission in Some Cases
• Correlations are Strong Between Different Aspects of Cognitive Decline
• A Caution Not to Forget the Continued Need for Fundamental Research into Aging
• Further Evidence for Cellular Senescence to Contribute to Atrial Fibrillation

Cellular Senescence as a Contributing Cause of Sarcopenia
https://www.fightaging.org/archives/2022/02/cellular-senescence-as-a-contributing-cause-of-sarcopenia/

Every age-related disease that can be linked to the chronic inflammation of aging is likely driven in part by the accumulation of senescent cells. This is not only a matter of senescent cells present in the organs affected by disease, but also involves the burden of cellular senescence throughout the body. When lingering in significant numbers, senescent cells cause harm via their inflammatory secretions, the senescence-associated secretory phenotype (SASP). Secreted inflammatory signals can travel widely through the body, rousing the immune system to overactivity, and changing cell behavior for the worse.

Sarcopenia is the characteristic loss of muscle mass and strength that takes place with age. Linking sarcopenia to chronic inflammation, and indeed to senescent cells, is a new idea in the sense that the modern focus on cellular senescence in aging only began in earnest a decade ago or so (after another prior decade of a few voices trying to get more researchers to take it seriously). With the development of senolytic therapies to selectively destroy senescent cells in full swing for a few years now, scientists have been writing papers on the plausible role of cellular senescence in sarcopenia. Today's open access materials are an example of the type.

Cellular Senescence in Sarcopenia: Possible Mechanisms and Therapeutic Potential

Aging promotes most degenerative pathologies in mammals, which are characterized by progressive decline of function at molecular, cellular, tissue, and organismal levels and account for a host of health care expenditures in both developing and developed nations. Sarcopenia is a prominent age-related disorder in musculoskeletal system. Defined as gradual and generalized chronic skeletal muscle disorder, sarcopenia involves accelerated loss of muscle mass, strength, and function, which is associated with increased adverse functional outcomes and evolutionally refers to muscle wasting accompanied by other geriatric syndromes.

More efforts have been made to clarify mechanisms underlying sarcopenia and new findings suggest that it may be feasible to delay age-related sarcopenia by modulating fundamental mechanisms such as cellular senescence. Cellular senescence refers to the essentially irreversible growth arrest mainly regulated by p53/p21CIP1 and p16INK4a/pRB pathways as organism ages, possibly detrimentally contributing to sarcopenia via muscle stem cells (MuSCs) dysfunction and the senescence-associated secretory phenotype (SASP). Cellular senescence may have beneficial functions in counteracting cancer progression, tissue regeneration, and wound healing.

By now diverse studies in mice and humans have established that targeting cellular senescence is a powerful strategy to alleviating sarcopenia. However, the mechanisms through which senescent cells contribute to sarcopenia progression need to be further researched. We review the possible mechanisms involved in muscle stem cells (MuSCs) dysfunction and the SASP resulting from cellular senescence, their associations with sarcopenia, current emerging therapeutic opportunities based on targeting cellular senescence relevant to sarcopenia, and potential paths to developing clinical interventions genetically or pharmacologically.

Continued Exploration of Age-Related Differences in the Human Gut Microbiome
https://www.fightaging.org/archives/2022/02/continued-exploration-of-age-related-differences-in-the-human-gut-microbiome/

The gut microbiome changes with age, a collection of microbial species that live in symbiosis with their host, helping to process food. Beneficial species that generate metabolites needed by tissues decline in number, while harmful inflammatory populations grow in number. There is a bidirectional relationship between the aging of the immune system and the aging of the gut microbiome. The immune system is responsible for removing problem microbes, and when it falters in this task, the microbiome becomes more harmful to the host. In turn, problem microbes can trigger chronic inflammation, degrading immune function and tissue function. There are other issues involved in aging that negatively impact the relationship between body and microbiome, such as the declining integrity of the intestinal barrier, but immune system function is an important one.

The balance of populations in the human gut microbiome exhibits significant changes as early as mid-30s. A number of potential approaches exist to reverse these changes, some more proven and practicable than others. Fecal microbiota transplantation and flagellin immunization are probably the best of the options on the table: they are comparatively easily accomplished; there is supporting animal data; and these interventions are already tested to some degree in humans. In principle the right combination and amounts of probiotics should work, but I'm not aware of any great progress towards determining what those combinations and amounts should be, or even whether the necessary probiotics are presently manufactured at all. There is also little animal data to indicate anything more than modest benefits from present commonly used probiotics.

The small bowel microbiome changes significantly with age and aspects of the ageing process

The human gut microbiome, comprising bacteria, archaea, fungi, parasites, and viruses, has numerous, significant impacts on the physiology of the human host throughout its lifespan, including roles in nutrient absorption and metabolism, immune function, and even brain function and behavior. Following rapid colonization at birth, the gut microbiome undergoes dynamic changes during early childhood before settling into a relatively stable pattern that was thought to persist throughout adulthood, unless impacted by significant changes in diet, medications, or disease. However, recent studies have demonstrated that the gut microbiome changes with increasing age and that the diversity of the gut microbiome may influence longevity and healthy ageing.

A caveat is that these, like the majority of gut microbiome studies, relied on stool samples. Although stool is easier to procure and analyze, the small intestine is central to metabolism and the maintenance of homeostasis, and its microbial populations are significantly different from those in stool. Therefore, to explore the effects of ageing specifically on the small intestinal microbiome, we procured a total of 251 duodenal aspirates from subjects aged 18 to 80 years which had been collected as part of the REIMAGINE (Revealing the Entire Intestinal Microbiota and its Associations with the Genetic, Immunologic, and Neuroendocrine Ecosystem) study.

we demonstrate significant differences in the small intestinal microbiome in older subjects, using duodenal aspirates from 251 subjects aged 18-80 years. Differences included significantly decreased microbial diversity in older subjects, driven by increased relative abundance of phylum Proteobacteria, particularly family Enterobacteriaceae and coliform genera Escherichia and Klebsiella. Moreover, while this decreased diversity was associated with the 'ageing process' (comprising chronologic age, number of medications, and number of concomitant diseases), changes in certain taxa were found to be associated with number of medications alone (Klebsiella), number of diseases alone (Clostridium, Bilophila), or chronologic age alone (Escherichia, Lactobacillus, Enterococcus). Lastly, many taxa associated with increasing chronologic age were anaerobes.

In conclusion, this first examination of the effects of age and the ageing process on the small intestinal microbiome demonstrates that the duodenal microbiome changes with increasing age, with significant decreases in duodenal microbial diversity due to increased prevalence of phylum Proteobacteria, particularly coliforms and anaerobic taxa. Given the key roles of small intestinal microbes in nutrient absorption and host metabolism, these changes may be clinically relevant for human health during the ageing process.

Naked Mole Rats Exhibit Minimal Cardiac Aging
https://www.fightaging.org/archives/2022/02/naked-mole-rats-exhibit-minimal-cardiac-aging/

Naked mole rats exhibit negligible senescence, meaning that that individuals show a minimal functional decline as a result of aging until very late life. They exhibit a very low incidence of cancer. They are one of the most studied species in the context of the comparative biology of aging, the search for longevity assurance mechanisms in unusually long-lived species that might become the basis for therapies to treat aging in humans. That naked mole rats are mammals gives the hope that any discoveries are more likely to be relevant to our species than is the case for investigations of lower animals, such as the work on exceptional regeneration in salamanders or zebrafish.

In today's open access paper, the authors discuss heart function in aging naked mole rats. There is little speculation on mechanisms; the researchers involved only measured heart function. As is the case for most biological systems in the naked mole rat, an old heart performs about as well as a young heart. We know from other research that the harmful accumulation of senescent cells with age contributes to cardiac fibrosis and hypertrophy in mammals, while senescent cell behavior is unusually innocuous in naked mole rats. Other relevant issues that are less well investigated in the naked mole rat include calcification of cardiac tissue (where senescent cells also play a role, it seems) and stiffening of arteries due to cross-linking and other causes. It remains to be seen as to what can be learned from all of this.

Naked mole-rats maintain cardiac function and body composition well into their fourth decade of life

The prevalence of cardiovascular disease increases exponentially with age, highlighting the contribution of aging mechanisms to cardiac diseases. Although model organisms which share human disease pathologies can elucidate mechanisms driving disease, they do not provide us with innate examples how cardiac aging might be slowed or attenuated. The identification of animal models that preserve cardiac function throughout most of life offers an alternative approach to study mechanisms which might slow cardiac aging. One such species may be the naked mole-rat (NMR), a mouse-sized (40 g) rodent with extraordinary longevity (more than 37 years), and constant mortality hazard over its four decades of life.

We used a cross-sectional study design to measure a range of physiological parameters in NMRs between 2 and 34 years of age and compared these findings with those of mice aged between 3 months and 2.5 years. We observed a rapid decline in body fat content and bone mineral density in old mice, but no changes in NMRs. Similarly, rhythm disorders (premature atrial and ventricular complexes) occurred in aged mice but not in NMRs. Magnetic resonance and ultrasound imaging showed age-dependent increases in cardiac hypertrophy and diastolic dysfunction in mice which were absent in NMRs. Finally, cardiac stress tests showed an age-dependent decline in normalized cardiac output in mice, which was absent in NMRs.

This study demonstrates that unlike mice that exhibit pronounced declines in body composition and cardiac function commencing shortly after sexual maturity, NMRs can maintain tissue homeostasis throughout their four-decade long maximum lifespan. Furthermore, NMRs do not show any signs of diastolic dysfunction or cardiac hypertrophy and maintain similar functional cardiac reserve capacity at advanced age to that exhibited when young adults, at the prime of life. Collectively, these data reveal that the naked mole-rat provides a proof-of-concept that age-related declines in body composition and cardiac function are not inevitable. Elucidating these mechanisms may lead to the discovery of therapies to reduce the burden of age-associated cardiovascular pathology, morbidity, and mortality and thereby enhance quality of life in older humans.

Autophagy in the Context of Immune System Aging
https://www.fightaging.org/archives/2022/02/autophagy-in-the-context-of-immune-system-aging/

Autophagy is the name given to a collection of cellular maintenance processes that identify and break down worn and unwanted proteins and structures in the cell. More efficient autophagy in principle produces better cell and tissue function, and, over the long term, slower aging. A sizable portion of the research community is interested in autophagy in the context of aging, but outside the development of calorie restriction mimetic drugs, few groups are working towards therapies intended to upregulate autophagy in a targeted fashion. A program in the Life Biosciences portfolio is one of the limited number of examples.

The ability of calorie restriction to lengthen healthy life in short-lived species is largely the reason that autophagy became interesting, though many approaches that slow aging in animal studies are characterized by upregulation of autophagy. In the case of calorie restriction, extension of life span depends on the correct operation of autophagy. A good number of studies provide other evidence that points to improved autophagy as the primary cause of health and longevity benefits resulting from a reduced calorie intake.

One of the many benefits produced by calorie restriction, and calorie restriction mimetics capable of upregulating autophagy, is a slowed decline of the immune system in later life. With this in mind, today's open access paper discusses the relationship between autophagy and immune aging. As in other considerations of autophagy, it is plausible that the more important portion of autophagic activity is the removal of worn and damaged mitochondria, the selective autophagy known as mitophagy. Mitochondria decline in effectiveness with age, in large part due to faltering mitophagy. This has detrimental effects throughout the body that include altered behaviors and capabilities of immune cells.

Autophagy takes it all - autophagy inducers target immune aging

Recently, a plethora of studies revealed that selective autophagy, in close association with immunometabolism, is key in modulating immunity and immune cell dynamics. In addition, autophagy is further involved in differentiation and proliferation of immune cells, although what exactly underlies molecular mechanisms remains partly elusive. Mounting evidence indicates that mitophagy, which encompasses selective degradation of damaged or excessive mitochondria, is an especially crucial regulator of innate immune cell function. Autophagy also prevents mitochondrial DNA escaping into the cytoplasm by maintaining mitochondrial homeostasis, which inhibits initiation of type I interferon signalling and, ultimately, inflammation. Furthermore, autophagy is essential for T cell immunity and its decline with age leads to immunosenescence.

During the last two decades, several trailblazing studies have suggested that innate and adaptive immunity are key to fight not only infectious diseases but also non-communicable diseases including typical age-related conditions, such as cancer. Considering that autophagy facilitates adaptive immune cell activation and differentiation, and partially reverses systemic immunosenescence via modulating T cell immunity, clinical implementation of autophagy inducers provides high therapeutic potential.

Drug discovery has identified numerous small compounds that can reverse age-associated effects via autophagy. These have been suggested to extend median and maximal lifespan, underpinned by in vivo and in vitro data obtained in various animal models. Importantly, lifestyle and nutrition, particularly exercise and dietary restriction enhance the autophagy pathway. Several repurposed and already FDA-approved drugs that either inhibit mTORC1 or activate AMPK have recently gained considerable attention as promising immunoprotective interventions that could be translated into clinic within the next decade. Here, we focus on the three most-promising drugs (rapamycin, metformin, and spermadine) and on dietary restriction as a lifestyle change.

Two Years of Calorie Restriction Produces Thymic Regrowth in Humans
https://www.fightaging.org/archives/2022/02/two-years-of-calorie-restriction-produces-thymic-regrowth-in-humans/

The thymus is responsible for turning thymocytes produced in the bone marrow into T cells of the adaptive immune system, in a complicated process of selection. This system is highly productive in youth, but active thymic tissue atrophies with age. This occurs for reasons that are far from fully explored, but may involve complex systemic issues related to rising inflammation and ongoing exposure to pathogens. As the thymus atrophies, the supply of T cells diminishes, and this loss of reinforcements is one of the major causes of immune aging. The T cell component becomes ever more full of exhausted, damaged, misconfigured, and senescent cells.

In this context, today's research materials are very interesting indeed. The authors report on their demonstration that a couple of years of mild calorie restriction in humans (a 14% reduction in calorie intake) can produce regrowth of the atrophied thymus. A very striking cross-sectional MRI image is provided in the publicity materials. The researchers go into some detail as to which of the countless metabolic changes produced in response to a reduced calorie intake are responsible for these effects. They point to PLA2G7 downregulation, which may be a target for future therapies to mimic this outcome. That PA2G7 downregulation suppresses inflammation is a point of support for inflammation-centric hypotheses of age-related thymic atrophy.

The study includes imaging and metrics for the thymus, but looks to be light on important details regarding the T cell output of the thymus and related immune system parameters. Unfortunately, this is par for the course in studies of thymus regrowth and resulting restoration of more youthful T cell production. Researchers either measure the size and structure of the thymus, or the relevant immune system parameters, and almost never both of these items in the same study.

Calorie restriction trial reveals key factors in extending human health

New research is based on results from the Comprehensive Assessment of Long-term Effects of Reducing Intake of Energy (CALERIE) clinical trial, the first controlled study of calorie restriction in healthy humans. For the trial, researchers first established baseline calorie intake among more than 200 study participants. The researchers then asked a share of those participants to reduce their calorie intake by 14% while the rest continued to eat as usual, and analyzed the long-term health effects of calorie restriction over the next two years.

The team started by analyzing the thymus, a gland that sits above the heart and produces T cells, a type of white blood cell and an essential part of the immune system. The thymus ages at a faster rate than other organs. By the time healthy adults reach the age of 40, 70% of the thymus is already fatty and nonfunctional. And as it ages, the thymus produces fewer T cells.

The research team used magnetic resonance imaging (MRI) to determine if there were functional differences between the thymus glands of those who were restricting calories and those who were not. They found that the thymus glands in participants with limited calorie intake had less fat and greater functional volume after two years of calorie restriction, meaning they were producing more T cells than they were at the start of the study. But participants who weren't restricting their calories had no change in functional volume.

The researchers then honed in on the gene for PLA2G7, was one of the genes significantly inhibited following calorie restriction. PLA2G7 is a protein produced by immune cells known as macrophages. This change in PLA2G7 gene expression observed in participants who were limiting their calorie intake suggested the protein might be linked to the effects of calorie restriction. To better understand if PLA2G7 caused some of the effects observed with calorie restriction, the researchers also tracked what happened when the protein was reduced in mice in a laboratory experiment.

Reducing PLA2G7 in mice yielded benefits that were similar to what we saw with calorie restriction in humans. Specifically, the thymus glands of these mice were functional for a longer time, the mice were protected from diet-induced weight gain, and they were protected from age-related inflammation. These effects occurred because PLA2G7 targets a specific mechanism of inflammation called the NLRP3 inflammasome. Lowering PLA2G7 protected aged mice from inflammation.

Caloric restriction in humans reveals immunometabolic regulators of health span

The extension of life span driven by 40% caloric restriction (CR) in rodents causes trade-offs in growth, reproduction, and immune defense that make it difficult to identify therapeutically relevant CR-mimetic targets. We report that about 14% CR for 2 years in healthy humans improved thymopoiesis and was correlated with mobilization of intrathymic ectopic lipid. CR-induced transcriptional reprogramming in adipose tissue implicated pathways regulating mitochondrial bioenergetics, anti-inflammatory responses, and longevity. Expression of the gene Pla2g7 is inhibited in humans undergoing CR. Deletion of Pla2g7 in mice showed decreased thymic lipoatrophy, protection against age-related inflammation, lowered NLRP3 inflammasome activation, and improved metabolic health. Therefore, the reduction of PLA2G7 may mediate the immunometabolic effects of CR and could potentially be harnessed to lower inflammation and extend the health span.

Gene Therapy Delivering the Longevity-Associated Variant of BPIFB4 Improves Immune Function in Old Mice
https://www.fightaging.org/archives/2022/02/gene-therapy-delivering-the-longevity-associated-variant-of-bpifb4-improves-immune-function-in-old-mice/

In recent years, researchers have identified a variant of the gene BPIFB4 that correlates with longevity in humans, and in mice appears to suppress mechanisms in immune cells that contribute to chronic inflammation. In this paper, researchers use gene therapy to deliver the longevity-associated variant of BPIFB4 to old mice, and find that it reduces the presence of inflammatory immune cells showing markers of cellular senescence. The chronic inflammation of aging is known to contribute to many different age-related conditions, and the growing presence of senescent cells provides a sizable fraction of that inflammatory signaling. It is an important goal to find ways to suppress it without interfering in the necessary short-term inflammation needed to respond to infection and injury.

As we age, our body experiences chronic, systemic inflammation contributing to the morbidity and mortality of the elderly. The senescent immune system has been described to have a causal role in driving systemic aging and therefore may represent a key therapeutic target to prevent pathological consequences associated with aging and extend a healthy lifespan. Previous studies from our group associated a polymorphic haplotype variant in the BPIFB4 gene (LAV-BPIFB4) with exceptional longevity. Transfer of the LAV-BPIFB4 in preclinical models halted the progression of cardiovascular diseases (CVDs) and frailty by counterbalancing chronic inflammation.

In the present study, we aimed to delineate the action of systemic adeno-associated viral vector-mediated LAV-BPIFB4 gene transfer (AAV-LAV-BPIFB4) on the deleterious age-related changes of the immune system and thereby the senescence-associated events occurring in C57BL/6J mice aged 26 months. Our in vivo data showed that 26-months-old mice had a higher frequency of CD45+SA-beta Gal+ immune cells in peripheral blood than young (4-months-old) C57BL/6J mice. Notably, AAV-LAV-BPIFB4 gene transfer in aged mice reduced the pool of peripheral immunosenescent cells that were shown to be enriched in the spleen. In addition, the proper tuning of the immune secretory phenotype (IL1βlow, IL6low, IL10high) associated with a significant reduction in SA-beta Gal-positive area of aorta from AAV-LAV treated mice.

At the functional level, the reduction of senescence-associated inflammation ensured sustained NAD+ levels in the plasma of AAV-LAV-BPIFB4 old mice by preventing CD38 increase in F4/80+ tissue-resident macrophages and Ly6Chigh pro-inflammatory monocytes of the spleen and bone marrow. Finally, to validate the clinical implication of our findings, we showed that Long-living-individuals (LLIs, older than 95 years), which delay CVDs onset, especially if LAV-carriers, were characterized by high NAD+ levels. In conclusion, the new senotherapeutic action of LAV-BPIFB4 may offer a valuable therapeutic tool to control aging and reduce the burden of its pathophysiological disorders, such as CVDs.

Activated Protein C Activity is Impaired in Aging Hearts, Leading to Greater Vulnerability to Ischemia
https://www.fightaging.org/archives/2022/02/activated-protein-c-activity-is-impaired-in-aging-hearts-leading-to-greater-vulnerability-to-ischemia/

Researchers here show that activated protein C (APC) is involved in the mechanisms that cause cell death and dysfunction subsequent to ischemia, the temporary loss of flow of blood to tissue, and reperfusion, the return of that supply. Much of the harm following a heart attack or stroke might be avoided if cells just behaved differently. Researchers found that APC activity is reduced in old tissues, and this makes cells more vulnerable. Upregulation of APC may help to somewhat reduce the consequences of ischemia.

APC, a protein circulating in blood, has both anticoagulant (blood clot prevention) and anti-inflammatory functions that can help protect cells from disease and injury. Endothelial protein C receptor (EPCR) - located both on cells lining blood vessels and on the surface of cell membranes, including heart muscle cells - is associated with increased APC production and regulates APC's subsequent cell signaling (or cell communication).

The stress of ischemia and reperfusion injury induced "shedding" of EPCRs in young and old wild-type mice - that is, a greater number of these receptors were cut from the heart muscle cell membrane and then moved into the bloodstream. This EPCR shortage (deficiency) in the heart can impair activated protein C signaling critical for favorably regulating energy metabolism and anti-inflammatory responses, preventing cell death, and stimulating other activities needed to protect cardiac muscle cells. While the hearts of the old and young wild-type mice both showed EPCR shedding, older hearts experienced a more severe EPCR deficiency and decline in APC signaling activity in response to reperfusion injury.

Administering APC or its derivatives helped reduce heart damage inflicted by ischemia and reperfusion, particularly in the old mice. Digging deeper, the researchers discovered that by stabilizing (maintaining) EPCR on the cardiac cell membrane, APC strengthens the aging heart's resistance both to heart attack-related ischemia and to injury associated with restoring coronary artery blood flow.

The researchers detailed how APC treatments improve cardiac function by regulating both acute (short-term) and chronic (longer-term) metabolic pathways. They demonstrated that enzyme AMPK (AMP-activated protein kinase) mediates an acute adaptive response to cardiac stress immediately following heart attack, while enzyme AKT (protein kinase B) regulates chronic metabolic adjustments to reperfusion stress over time. APC treatment led to better enzyme activity and more efficient energy balance needed to contract cardiac muscle cells and pump blood from the heart to the rest of the body.

Aquaporin-4 Expression in the Aging Choroid Plexus
https://www.fightaging.org/archives/2022/02/aquaporin-4-expression-in-the-aging-choroid-plexus/

Researchers here discuss the rising expression of aquaporin-4 in the vasculature of the aging brain, particularly the choroid plexus, where cerebrospinal fluid is produced. That production decreases with age. Aquaporin-4 is one of a family of proteins that facilitates transfer of water through cell membranes, and it is an important part of the regulation of fluid in the brain. It is unclear as to whether this rising expression is (a) harmful, one of many detrimental alterations that take place in the aging vasculature and brain structures, and a contributing cause of reduced cerebrospinal fluid production, or (b) an ultimately unsuccessful attempt to compensate for some of those harms by increasing cerebrospinal fluid production.

The choroid plexus (CP) consists of specialized ependymal cells and underlying blood vessels and stroma producing the bulk of the cerebrospinal fluid (CSF). CP epithelial cells (CPCs) are considered the site of the internal blood-cerebrospinal fluid barrier, show epithelial characteristics (basal lamina, tight junctions), and express aquaporin-1 (AQP1) apically. In this study, we analyzed the expression of aquaporins in the human CP. As previously reported, AQP1 was expressed apically in CPCs. Surprisingly, and previously unknown, many cells in the CP epithelium were also positive for aquaporin-4 (AQP4), normally restricted to ventricle-lining ependymal cells and astrocytes in the brain.

Expression of AQP1 and AQP4 was found in the CP of all eight body donors investigated (age 74-91). We hypothesized that AQP4 expression in the CP was caused by age-related changes. To address this, we investigated mouse brains from young (2 months), adult (12 months) and old (30 months) mice. We found a significant increase of AQP4 mRNA in old mice compared to young and adult animals.

In the context of the morphological and functional changes associated with age and disease in the CP, the detection of AQP4 in CPCs and can be interpreted in two alternative scenarios. First, AQP4 expression could serve as a compensatory mechanism in old age to maintain CSF production known to be decreased. An alternative hypothesis can be inferred from AQP4 expression in the ependyma adjacent to the plexus epithelium. Here, AQP4 is expressed in the basolateral membrane domain of ependymal cells. Therefore, CPCs might differentiate over time into AQP4-positive cells, and the expression of AQP4 leads to an inverted transcellular water flow resulting in a reduced CSF production.

Improved Physical Function in Old Mice Treated with Rapamycin, Acarbose, and Phenylbutyrate
https://www.fightaging.org/archives/2022/02/improved-physical-function-in-old-mice-treated-with-rapamycin-acarbose-and-phenylbutyrate/

It is quite rare for researchers to attempt combined treatments, unfortunately. The panoply of calorie restriction mimetics and other approaches to gently upregulate stress responses are individually not all that impressive, and it remains unclear as to which of them can be stacked for greater effect. In the treatment of aging, even the better approaches that produce actual and rapid rejuvenation, such as senolytic therapies to destroy senescent cells, will have to be stacked with one another. There are many different contributing causes of aging. Here, researchers report that a combination therapy carried out for a few months in aged mice produces improvements of 20-40% in physical function. That duration corresponds, very roughly, to a decade or more of sustained treatment in old humans.

Loss of physical performance, as seen in humans by decreased grip strength and overall physical fitness, is generally accepted to be a consequence of aging. Treatments to delay or reduce these changes or increase resilience to them are generally not available. In this preliminary study, 20-month-old male and female C57BL/6 mice were given either a standard mouse diet or a formulated mouse diet containing rapamycin (14 ppm), acarbose (1000 ppm), and phenylbutyrate (1000 ppm), or a diet containing one half dose of each drug, for 3 months. At the end of the study, performance on a rotarod and grip strength test was compared.

Rapamycin blocks mTOR, a protein shown to integrate signals from growth factors and nutrients to control protein synthesis. The anti-aging effect of downregulating mTOR was confirmed by the NIA Intervention Testing Program showing that rapamycin extended lifespan in mice. Arcabose is a popular type 2 diabetes medication used for glucoregulatory control, and it also increases mouse lifespan. Phenylbutyrate is clinically approved as an ammonia scavenger for urea cycle disorders in children, and is also an inhibitor of histone deacetylase. In aging mice, it enhances physical and cognitive performance.

In general, mice fed the full dose drug cocktail diet performed better on these assays, with significant improvements in rotarod performance in females fed the full dose cocktail and in grip strength in males fed the full dose cocktail, and females fed the low dose cocktail. These observations provide support for the concept that short term treatment with a cocktail of drugs that targets multiple aging pathways can increase resilience to aging, and suggests that this prototype cocktail could be part of a clinical therapeutic strategy for delaying age-related loss of physical performance in people.

More Animal Study Evidence for Senolytics to Improve Cognitive Function in Old Age
https://www.fightaging.org/archives/2022/02/more-animal-study-evidence-for-senolytics-to-improve-cognitive-function-in-old-age/

A growing number of rodent studies have demonstrated the ability of senolytics to improve cognitive function in old animals by clearing a sizable fraction of lingering senescent cells from aged tissues throughout the body. Specifically this means the dasatinib and quercetin combination, as both can cross the blood-brain barrier after oral administration. Researchers have undertaken a study in Alzheimer's patients, but it will be quite some time before results are published. Senescent cells generate inflammatory signaling, and inflammation in brain tissue is strongly implicated in the progression of neurodegenerative conditions. The degree to which this is the result of the activity of senescent cells in the brain versus the signaling of the many more senescent cells outside the brain is up for debate. Clearing such cells globally is in any case clearly beneficial in rodents.

Aging is associated with cognitive decline and accumulation of senescent cells in various tissues and organs. Senolytic agents such as dasatinib and quercetin (D+Q) in combination have been shown to target senescent cells and ameliorate symptoms of aging-related disorders in mouse models. However, the mechanisms by which senolytics improve cognitive impairments have not been fully elucidated particularly in species other than mice.

To study the effect of senolytics on aging-related multifactorial cognitive dysfunctions we tested the spatial memory of male Wistar rats in an active allothetic place avoidance task. Here we report that 8 weeks treatment with D+Q alleviated learning deficits and memory impairment observed in aged animals. Furthermore, treatment with D+Q resulted in a reduction of the peripheral inflammation measured by the levels of serum inflammatory mediators (including members of senescent cell secretome) in aged rats.

Significant improvements in cognitive abilities observed in aged rats upon treatment with D+Q were associated with changes in the dendritic spine morphology of the apical dendritic tree from the hippocampal CA1 neurons and changes in the level of histone H3 trimethylation at lysine 9 and 27 in the hippocampus. The beneficial effects of D+Q on learning and memory in aged rats were long-lasting and persisted at least 5 weeks after the cessation of the drugs administration.

25-Hydroxycholesterol as a Basis for Senolytic Therapy
https://www.fightaging.org/archives/2022/02/25-hydroxycholesterol-as-a-basis-for-senolytic-therapy/

25-hydroxycholesterol is an oxidized form of cholesterol, and researchers here demonstrate that it is senolytic to some degree in mice. This may be competitive with existing first generation senolytics; from the paper, it looks like it clears about half of the excess of senescent cells present in old mice, in muscle tissue at least. Like all other senolytics, its effectiveness likely varies widely by tissue type and location in the body. Oxidized cholesterols are largely thought to be harmful in the body, particularly because they can cause macrophages to become dysfunctional and accelerate the progression of atherosclerosis. It is unclear as to whether that could prove to be a blocking issue at the sort of doses and schedules used in senolytic therapy.

Researchers have shown that the endogenous metabolite 25-hydroxycholesterol (25HC) significantly reduced the burden of senescent cells in multiple cell types in both mice and human cell culture, and in live mice, where it showed particular efficacy in skeletal muscle. "Given that 25HC shares no common molecular motifs with other senolytics, it appears that this molecule represents a brand new class of potential interventions."

25HC is a little understood oxidized lipid involved in cholesterol metabolism. The team identified it after discovering that the molecule disrupted cellular senescence in CRYAB, a small heat shock protein which was upregulated upon senescence in nine different cell types from two species, mice and humans. Diseases associated with CRYAB include myopathies, diseases that affect muscles that control voluntary movement in the body.

Working in mouse and human cell cultures researchers isolated specific cell types from skeletal muscle, made them senescent and showed that 25HC could kill them selectively. The team then went on to test 25HC in aged mice; experiments showed 25HC improved their muscle mass. Researchers also determined that 25HC killed senescent cells in mouse dermal fibroblasts, and in primary human cells from the lung, heart, liver, kidney, and articular cartilage. "We are intending to use this molecule in multiple paradigms of aging and we're hoping that other researchers will start testing it as well."

Early CAR-T Therapies Produced Long Term Remission in Some Cases
https://www.fightaging.org/archives/2022/02/early-car-t-therapies-produced-long-term-remission-in-some-cases/

Much of what we'd like to know about cancer therapies takes a long time to emerge. Only now is the long term data available for the first CAR-T immunotherapies aimed at forms of leukemia in which cancerous cells are clearly and distinctly marked by characteristic surface features. The field has long since expanded, and researchers are at present trying to adjust CAR-T in order to apply this form of treatment to solid cancers. Long term remission is not the same as a cure, as cancer is a disease in which it remains challenging to say whether or not a few remnant cancer cells await a return at some future time. If one can make it ten years in remission, with no sign of cancer, however, that may well be a cure under the hood, the cancer gone and never to return.

The year was 2010, and Olson was one of the first people with chronic lymphocytic leukaemia to receive the treatment, called CAR-T cell therapy. When his doctors wrote the protocol for the clinical trial that Olson was involved in, they hoped that the genetically engineered cells might survive for a month in his body. They knew that cancer research could be heartbreaking; they didn't dare to expect a cure. But more than ten years later, the immune cells continue to patrol Olson's blood and he remains in remission. Doctors finally ready to admit what Olson suspected all along. "We can now conclude that CAR T cells can actually cure patients with leukaemia."

CAR-T cell therapies involve removing immune cells called T cells from a person with cancer, and genetically altering them so that they produce proteins - called chimeric antigen receptors, or CARs - that recognize cancer cells. The cells are then reinfused into the person, in the hope that they will seek out and destroy tumours. In the years since Olson's treatment, five CAR-T cell therapies have been approved by the US Food and Drug Administration, to treat leukaemias, lymphomas, and myelomas. It is estimated that tens of thousands of people have received CAR-T cell treatment.

But the therapy is expensive, risky and technically demanding. It remains a last resort, to be used when all other treatments have failed. Despite the treatment's success for Olson, not everyone experiences durable remission of their cancer. In the beginning, only about 25-35% of CAR-T cell recipients with chronic lymphocytic leukaemia experienced a complete remission of their cancer. With refinement, that percentage has increased over the years, he says, but some of these initial successes still lead to relapse. Tracking the treatment long-term could reveal clues as to what factors are important for lasting CAR-T cell success.

Correlations are Strong Between Different Aspects of Cognitive Decline
https://www.fightaging.org/archives/2022/02/correlations-are-strong-between-different-aspects-of-cognitive-decline/

The evidence from this study points to a tight coupling between age-related losses in different areas of cognitive function. This is more or less what one might expect to occur in a complex system that is undergoing chemical and small-scale structural damage. Such damage will tend to affect all emergent properties of the system. The goal of medical research and development should be to find ways to repair that damage and restore function, not attempt to otherwise compensate for ongoing losses.

At the age of 20, people usually find it easier to learn something new than at the age of 70. People aged 70, however, typically know more about the world than those aged 20. In lifespan psychology this is known as the difference between "fluid" and "crystallized" cognitive abilities. Fluid abilities primarily capture individual differences in brain integrity at the time of measurement, whereas crystallized abilities primarily capture individual differences in accumulated knowledge.

Accordingly, fluid and crystallized abilities differ in their average age trajectories. Fluid abilities like memory already start to decline in middle adulthood. In contrast. crystallized abilities such as vocabulary show increases until later adulthood and only evince decline in advanced old age. This divergence in the average trajectories of fluid and crystallized abilities has led to the assumption that people can compensate for fluid losses with crystallized gains. A study now shows that this compensation hypothesis has more limits than previously claimed.

The correlations between the two types of changes observed were very high. Thus, individual differences in cognitive development are, to a large extent, domain-general and do not follow the fluid-crystallized divide. What this means is that individuals who show greater losses in fluid abilities simultaneously show smaller gains in crystallized abilities, and persons whose fluid abilities hardly decline show large gains in crystallized abilities. These findings are in accordance with the everyday observation that some people remain mentally fit in many areas into very old age while others' cognitive functioning declines across the board. People whose memory is declining, also show a low gain in knowledge, even though they are in most need of such gains. Conversely, individuals with small fluid losses and strong crystallized gains are less likely to be in need of relying on compensatory processes to begin with.

A Caution Not to Forget the Continued Need for Fundamental Research into Aging
https://www.fightaging.org/archives/2022/02/a-caution-not-to-forget-the-continued-need-for-fundamental-research-into-aging/

A growing longevity industry is picking up ongoing academic projects in increasing numbers and working towards the clinical availability of therapies to treat aging. Amidst all the light and noise, one of the researchers in the field here asks for us not to overlook the need for more fundamental research. I agree, though I'd say that the most important portion of research not to be overlooked are the projects in the SENS rejuvenation biotechnology portfolio yet to make it to enthusiastic commercial development. To my eyes, the fastest way to find out more about how aging works is to implement and test specific rejuvenation strategies, each of which addresses only a narrow aspect of aging.

João Pedro de Magalhães has dedicated his career to understanding the biological puzzle of aging. With so much focus now being placed on developing new interventions in the longevity field, de Magalhães is concerned that the fundamental research into understanding why we age may be taking more of a back seat. "What you see in the field as a whole is that it's on an upwards trajectory, which makes it very exciting. I remember the first conference I went to in the field of aging, which must have been 20 years ago when I was a PhD student and there were only a couple of companies starting to work on aging. So it's impressive how much the field has grown in the past 20 years - it's really remarkable. Which is really about more and more people recognising aging as something that can be intervened in."

"I think on one hand that this is very exciting. But on the other hand, I also think it shows there has been a shift in the field away from studying mechanisms of aging. I'm not saying everybody's doing this, but, as a field, it's almost like we're giving up on trying to understand why we age and instead focus on the fact that we can manipulate aging in model systems and identifying interventions and therapies and drugs. I'm sure that we're going to develop therapies that work and it will be fantastic, from a health perspective, from a financial perspective and so on. But I also think most of what we're discovering, at the basic science level at the preclinical level is not going to work in humans. So I believe we still have to go after the difficult questions and the difficult problems, such as why we age. Let's go after the high-hanging fruit!"

Illustrating his concern in this area, de Magalhães points to a paper he co-authored with David Gems last year, which criticises the hallmarks of aging. "It's one of the articles I'm most proud of, because, although it may not make everybody happy, it's highlighting this issue, which is, in my view, the hallmarks are an oversimplification. In reality, there's still a lot of work to do to understand the process of aging, which is still very poorly understood. Even though it's not a low hanging fruit, even though it's difficult, we still need to have a better understanding of the mechanistic causes of aging, which, in my view, the hallmarks of aging does not provide."

Further Evidence for Cellular Senescence to Contribute to Atrial Fibrillation
https://www.fightaging.org/archives/2022/02/further-evidence-for-cellular-senescence-to-contribute-to-atrial-fibrillation/

Senescent cells accumulate with age, and their secretions provoke chronic inflammation and tissue dysfunction. With this in mind, researchers have shown that cellular senescence correlates with atrial fibrillation in older people. Here is a more recent demonstration of this relationship. I'm not aware of a study that shows senolytic therapy to remove senescent cells is a useful treatment for atrial fibrillation, but evaluation of this approach seems a good idea, both in aged animal models and in human patients.

Atrial fibrillation (AF) is the most frequent arrhythmia in clinical practice and is closely associated with increased cardiovascular morbidity and mortality. Accumulating evidence has shown that the incidence and prevalence of AF increase with age. Moreover, aging is an important risk factor for AF recurrence. At the cellular level, aging is characterized by cellular senescence, a state of irreversible cell cycle arrest and loss of specialized cellular functions. Senescent cells accumulate with age; as a result of genotoxic stress or various chronic diseases, they contribute to tissue aging and have been implicated in age-related tissue dysfunction because of the accumulation of damaged cells at sites of tissue injury and remodeling.

Recently, researchers have investigated the link between AF and cell senescence, showing that endothelial or fibroblast senescence may pave the way for adverse atrial remodeling in AF by promoting proinflammatory, prothrombotic, and profibrotic responses. We sought to understand senescence in AF and the extent to which it aggravates the AF process. Twenty-six AF patients undergoing open-heart surgery were included, and 12 patients with sinus rhythm served as controls. Another cohort included 120 consecutive persistent AF patients with valvular heart diseases.

Compared with sinus rhythm, left atrial appendages (LAAs) with AF presented a significantly increased positive area of cellular senescence, with upregulated expression of p16, p21, and p53. Next, p21 mRNA was increased in patients with AF recurrence compared with that in patients without recurrence. Further, p21 was a significant independent predictor of AF early recurrence (odds ratio 2.97). This finding may help facilitate the search for new therapeutic approaches for antiaging therapy for AF.